Photodiodes comprise of multiple radiation sensitive junctions formed in semiconductor material. Within a photodiode, charge carriers are created by light that illuminates the junction and photocurrent is generated dependent upon the degree of illumination. Similarly, a photodiode array comprises of large numbers of light sensitive spaced-apart elements, further comprising of a semiconductor junction and a region of high response where the photo-generated charge carriers are collected. Arrays of photodiodes or basically photodiodes are used in various applications including, but not limited to, optical position encoding, and low light-level imaging, such as night photography, nuclear medical imaging, photon medical imaging, multi-slice computer tomography (CT) imaging, radiation detection and ballistic photon detection.
Photodiodes are characterized by certain characteristics, such as electrical, optical, current (I), voltage (V), and noise. Electrical characteristics of photodiode dominantly include shunt resistance, series resistance, junction capacitance, rise or fall time and frequency response. Noise in photodiodes is generated by a plurality of sources including, but not limited to, thermal noise, quantum or photon noise, and flicker noise. Also, silicon photodiodes, essentially active solid-state semiconductor devices, are among the most popular photodetectors coalescing high performance over a wide wavelength range with unmatched user-friendliness. For example, silicon photodiodes are sensitive to light in the wide spectral range, extending from deep ultraviolet all the way through visible to near infrared. Additionally, silicon photodiodes detect the presence or absence of minute light intensities thereby facilitating extremely precise measurement of the same on appropriate calibration. For instance, appropriately calibrated silicon photodiodes detect and measure light intensities varying over a wide range, from very minute light intensities of below 10-13 watts/cm2 to high intensities above 10-3 watts/cm2.
Accordingly, there is need in the prior art for a photodiode that can be used as an adjustable low pass or high pass wavelength filter detector. Specifically, there is need in the prior art for a front and back side PN-junction photodiode that is sensitive to wavelengths and can also be used as a high speed long wavelength detector at relatively low reverse bias.